These operators are declared in the namespace std::literals::chrono_literals, where both literals and chrono_literals are inline namespaces. Access to these operators can be gained with usingnamespace std::literals and usingnamespace std::literals::chrono_literals.

In addition, within the namespace std::chrono, the directive usingnamespace literals::chrono_literals; is provided by the standard library, so that if a programmer uses usingnamespace std::chrono; to gain access to the duration classes, the duration literal operators become visible as well.